The object of the invention is a valve designed to be fixed in tight fashion in the rim of a wheel to provide the air supply of a tubeless tire mounted on said rim and, more particularly, a valve designed to equip tire and rim assemblies including a pneumatic support membrane.
Patent Application FR 96/14631 discloses a belted pneumatic membrane, made of reinforced rubber, supporting the tread of a tubeless tire in case of puncture of the latter. This membrane is designed to be arranged in the inside of the inner cavity defined by the tire and its rim and to be inflated to a pressure greater than that of the cavity of the tire. Under these conditions of normal use, the membrane has a maximum running radius smaller than the loaded radius of the tire used at its recommended pressure. In case of puncture of the tire, when the pressure difference between the cavity of the membrane and that of the tire exceeds a given value, the membrane belt ruptures, the membrane is deployed into the assembly of the tire cavity and thus permits the tire to continue running under acceptable conditions.
Such a running tire, rim and support membrane assembly may include two separate inflation and deflation valves. This is the usual solution proposed for example by U.S. Pat. No. 5,538,061. However, this solution has two disadvantages. First of all, the presence of two valves is undesirable because this necessitates a second hole punched through the rim. On the other hand, these two valves do not protect the user from a handling error during a tire maintenance operation that might accidentally be caused by the pressure difference between the two cavities beyond the threshold value of rupture of the membrane reinforcement.
The subject of the invention is a valve that solves this problem.
The valve according to the invention is designed to equip a tire and rim assembly defining a first tight inner cavity, the said assembly comprising a pneumatic support membrane defining a second tight inner cavity arranged in the first tight inner cavity. This valve comprises:
a first passage connecting the second inner cavity and the open air;
a second passage connecting the said first passage and the first inner cavity;
a tight pneumatic chamber connected to the second passage;
first means of closure of the connection between the first and the second passage, such that the said connection is closed when the pressure difference between the said first passage and the said chamber is below a first given threshold; and
second means of closure of the connection between the pneumatic chamber and the second passage, such that the said connection is closed when the pressure in the said second passage is below a second given threshold.
Preferentially, the value of the first threshold corresponds approximately to the pressure difference in normal operation between the first and second cavities, and the second threshold is approximately equal to the rated inflation pressure of the tire when cold.
This valve has the advantage of permitting use very close to that of conventional valves: There is only one single inflation orifice; at the time of inflation, it suffices to reach the pressure provided for the cavity of the membrane for the cavity of the tire also to be at the rated inflation pressure, the connection between the two passages then being in closed position.
Preferably, the first passage comprises a nonreturn valve isolating the second tight cavity, that of the pneumatic support membrane, from the connecting passage between the two passages of the valve.
This valve thus makes it possible to guarantee complete pneumatic independence between the two cavities. In case of puncture, only the pressure in the first cavity diminishes.
The valve according to the invention, in an advantageous embodiment, includes means for simultaneous exposure to the open air of the two supply passages of the two pneumatic cavities. Deflation, being simultaneous, does not risk causing rupture of the reinforcement of the support membrane.